In automated mail sorting systems, the ZIP code of the destination address on post mail, e.g., a letter or a parcel, has to be found. This is usually done by evaluating a digital image of the relevant surface of the piece of mail. This evaluation comprises firstly a procedure called Address Block Location (ABL) which locates a portion of the surface which looks like an address block, or has at least some similarity to it. Then, this portion is selected and passed to an Optical Character Recogntion (OCR) system for further processing aimed to extract a ZIP code associated with the destination address of the post mail so that a sorting machine can sort the mail according to the ZIP code.
In prior art sorting machines, electronic programs running on a computer associated with the sorting machine are implemented to perform the ABL and said OCR procedures after a digital picture has been taken of the letter's or parcel's relevant surface area.
Such a system is disclosed in WO 98 17 405, the disclosure of which is incorporated by reference herein. The above-mentioned procedures are performed sequentially, first ABL, and then OCR. With a great portion of letters or parcels, such systems work quite well even though there remains an error rate which is always worth being lowered. Errors are very often due to confusing the destination address with the return address, both written on the surface.
Problems arise when the size of the envelope or one of the parcels is larger than about DIN B5, as may be the case, very often, particularly with parcels where further remarks, emblems, stamps or the like are printed on the surface. This can be misleading for such ABL systems because any of such emblems or remarks can be interpreted as a potential address block which is then passed to the OCR system and will be evaluated in vain as a destination address block.